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Biomedical subjects

D Brdiczka

Publications and source records attributed to D Brdiczka.

7 recordsLinked to original sources
PubMed1992

The cation-selective substate of the mitochondrial outer membrane pore: single-channel conductance and influence on intermembrane and peripheral kinases.

The polyanion-induced substate of the outer mitochondrial membrane was studied in vivo and in vitro. Study of the substate in artificial bilayers showed that it is highly cation selective. The induction of the substate in intact mitochondria leads to a complete inhibition of the intermembrane kinases, such as creatine kinase and adenylate kinase, which were excluded from the external ATP pool. Peripheral kinases, such as hexokinase, were blocked when they utilized internal ATP. The results with intact mitochondria suggested the existence of two regions of the outer membrane containing channels of different states, which may be involved in the regulation of intermembrane and peripheral kinases.

Adenosine Triphosphate↗
PubMed1978

On the occurence and composition of dense particles in mitochondria in ultrathin frozen dry sections.

Clusters of dense particles were observed irregularly in mitochondrial profiles of shock-frozen brown adipose tissue and liver when cryosectioned at a chamber temperature of -80 degrees C and not if sectioning was performed at -110 degrees C. The particles are rich in Ca and P (Ca/P =0.5); they are therefore not any form of tricalcium orthophosphate (e.g. hydroxyapatite). They apparently form by electrolyte diffusion in the section and therefore cannot be considered as representing the in vivo pool of mitochondrial calcium.

Adipose Tissue, Brown↗
PubMed1977

ATPase activities, Ca2+ transport and phosphoprotein formation in sarcoplasmic reticulum subfractions of fast and slow rabbit muscles.

Subfractionation of sarcoplasmic reticulum from fast-twitch and slow-twitch rabbit skeletal muscles was performed on a sucrose density gradient. Vesicle fractions were characterized by: measurement of (Ca2+,Mg2+)-dependent (extra) ATPase, Mg2+-dependent (basal) ATPase, Ca2+ uptake characteristics, polypeptide patterns in sodium dodecylsulphate polyacrylamide gel electrophoreses, phosphoprotein formation and electronmicroscopy of negatively stained samples. In fast-twitch muscle, low and high density vesicles were separated. The latter showed high activity of (Ca2+,Mg2+)-dependent ATPase, negligible activity of Mg2+-dependent ATPase, high initial rate and high capacity of Ca2+ uptake, high amount of phosphorylated 115000-Mr polypeptide, and appeared morphologically as thin-walled vesicles covered with particles of 4 nm in diameter. Low density vesicles had little (Ca2+,Mg2+)-dependent ATPase but high Mg2+-dependent ATPase. Although the initial rate of Ca2+ uptake was markedly lower, the total capacity of uptake was comparable with that of high density vesicles. Phosphorylated 115000-Mr polypeptide was detectable at low concentrations. Instead, 57000 and 47000-Mr polypeptides were characterized as forming stable phosphoproteins in the presence of ATP and Mg2+. Negatively stained, these vesicles appeared to have smooth surfaces. It is suggested that low density vesicles represent a Ca2+ sequestering system different from that of high density vesicles and that Mg2+-dependent (basal) ATPase as well as the 57000 and 47000-Mr polypeptides are part of the Ca2+ transport system within the low density vesicles. According to the results from slow-twitch muscle, Ca2+ sequestration by the sarcoplasmic reticulum functions in this muscle type only through the low density vesicles.

Adenosine Triphosphatases↗
PubMed1977

Raman spectroscopic investigation of the interaction of gramicidin A with dipalmitoyl phosphatidylcholine liposomes.

The interaction of gramicidin A with dipalmitoyl phosphatidylcholine liposomes is investigated by Laser-Raman spectroscopy. As revealed by the methylene C-H stretching mode the phase transition of the hydrocarbon chains near 40 degree C is eliminated in the presence of gramicidin A. Liposomes prepared from a mixture of lecithin and cholesterol seem to be unaffected by gramicidin A and show only the normal broadened phase transition.

Binding Sites↗
PubMed1976

Physical properties of muscle cell membranes during fusion. A fluorescence polarization study with the ionophore A23187.

1. The fluorescence polarization of A23187 is used to detect physical changes in myoblast membranes produced by Ca2+ concentrations which are able to trigger fusion. Temperature scans reveal a Ca2+-dependent fluidity increase in the microenvironment of the ionophore above 37 degree C. 2. Time-dependent polarization measurements show two different effects. The first one consists of a fast polarization increase which reaches its maximum after 5-10 min. This change could be explained by a Ca2+-induced phase separation of acidic and neutral phospholipids in the membrane. The second effect is a slow polarization decrease over 2-3 h subsequent to the fast increase. 3. The information derived from the fluorescence polarization is in accordance with the characteristics of the fusion of myoblast cells regarding the dependence on Ca2+ concentration, the inhibition by Mg2+ and lysolecithin as well as a typical temperature of 35-37 degree C where fusion rate changes abruptly.

Animals↗